Melt Preparation and Transfer MAGNESIUM IN …

1 1 Short Course_MgCOM2006, Montreal 11 MAGNESIUM IN METALLURGYMAGNESIUM IN METALLURGYMAGNESIUM IN METALLURGYH enry Hu, Materials ProgramDepartment of Mechanical, Automotive & Materials EngineeringUniversity of WindsorCASTINGCASTINGS hort Course_MgCOM2006, Montreal 22 OUTLINE Melt Preparation and Transfer Die casting Technologies Hot Chamber Cold Chamber ThixomoldingShort Course_MgCOM2006, Montreal 33Mg Alloy Phase DiagramAtomic % Aluminum10302020030040050070060020650304 0010 Weight % AlTypical casting Temperature Range630 - 650 oCAlloy Composition Al + + liquidTemperature CDie casting Alloys AZ91D AM60B AM50A,Short Course_MgCOM2006, Montreal 44 Melting Furnace for Mg AlloysShort Course_MgCOM2006, Montreal 55 Crucible for Holding Liquid MgMaterials: Cr-Mo Nickel Free Steel (life: 24 months) Laminated Cr Steel outer Shell (heating)Mild Steel Inner (life: 6-12 months) All Mild Steel (life: 6 months)Short Course_MgCOM2006, Montreal 66 Charging Ingots Prior to Melting Clean Dry Storage: - Dry to remove MgCO3 H2 OMgO + CO2+ H2O -> MgCO3 H2O Preheated (> 150 oC)2 Short Course_MgCOM2006, Montreal 77 Prevention of Melt Burning /Oxidization6506601107245005001000150020 0025003000 Temperature (C)Mg Melting Al Melting Mg Boiling Al BoilingShort Course_MgCOM2006, Montreal 88 Prevention of Melt Burning /OxidizationShort Course_MgCOM2006, Montreal 99 Prevention of Melt Burning /Oxidization Protective SF6+ COor SO2+ Dry AirDisadvantages: - Need crucible cover + gas mixing system- High concentration causes corrosion problems (if not used properly)- Not efficient at very high T- Green house effect - Health concerns (SO2)Advantages.

2 - No flux contamination- Lower % of metal loss- Non-toxic (SF6)- Create strong, thin metallic film- Small quantity needed if well distributed over the meltShort Course_MgCOM2006, Montreal 1010 Prevention of Melt Burning /Oxidization Salt , 50% MgCl, 30% KCl and 20% NaClProblems: Flux comtamination, corrosion, HCl fume, Cl2pollution Burning InhibitorsAddition of (5 ppm) BeShort Course_MgCOM2006, Montreal 1111 Hot Chamber Die CastingShort Course_MgCOM2006, Montreal 1212 Step 3. - Piston injects metal into 2. - Vacuum is applied to drawliquid metal up goose NeckPistonStep 4. - Part 6. - Feed gates aremachined off 5. - Vacuum is released, moldopened and part 1. -Mold is InCoolantOutCoolingLinesMoltenMetalBathM oldHot Chamber Die Casting3 Short Course_MgCOM2006, Montreal 1313 Hot Chamber Die CastingThe hot chamber process is used extensively for casting of smaller MAGNESIUM parts with shot weights up to 2-3 kilograms. This process is not used for aluminium parts.

3 Static metal pressures are usually less than in cold chamber machines,typically in the range of 20-30 MPa (2900-4400 psi).A typical wall thicknesses of castings is around mm for the complex stiffener frame or could be less than 1 mm for simple gemetries such as notebook computer and cellular phone Course_MgCOM2006, Montreal 1414 Vacuum is used to a limited extent in hot chamber MAGNESIUM die casting . The technical literature is limited as to the effect of vacuum assistance on the properties of MAGNESIUM die castings. Further investigations are needed to document the extent to which vacuum provides significant improvements of properties in MAGNESIUM die Chamber Die casting - VacuumShort Course_MgCOM2006, Montreal 1515 Hot Chamber Die casting - Applicationsnotebook , ToolShort Course_MgCOM2006, Montreal 1616 Cold Chamber Die casting Cell Layout Short Course_MgCOM2006, Montreal 1717 Cold Chamber Die casting Melt Transfer NADCAS hort Course_MgCOM2006, Montreal 1818 Cold Chamber Die Casting4 Short Course_MgCOM2006, Montreal 1919 Cold Chamber Die CastingStep 2.

4 - New and re-mixed alloyis injected into the 1. - Metal mold is closed andthe injector shot-chamber is InCoolant OutShot ChamberCoolingLinesStep 3. - Rapid solidificationof part under high 4. - Ejection of part & Course_MgCOM2006, Montreal 2020 Die casting : MAGNESIUM vs. AluminumAdvantages lower density for weight reduction(up to 50%) faster shot speed(up to 50%) longer die life(2-5 times) thinner wall casting (1 - 2 mm) lower machining cost(up to 40%)Disadvantages higher material cost ( times in volume) poorer high temperatureProperties lower elastic modulus more difficulties in scrap recyclingShort Course_MgCOM2006, Montreal 2121In general, the cold chamber die casting process, can be used for MAGNESIUM and aluminium alloys. However, the lower heat content in magnesiumcompared to aluminium is important to the die casting process. To avoid solidification of the MAGNESIUM alloy during die filling, a shorter fill time is required formagnesium than for aluminium.

5 For this reason, some MAGNESIUM die casters specify machine designs withmaximum shot plunger speeds exceeding 10 m/s. Static casting pressures are commonly in the range of 30- 70 MPa (4400-10000 psi). The locking force of themachine holding the two die halves together exceeding 4000 tons are commercially Chamber Die casting - MachinesShort Course_MgCOM2006, Montreal 2222 Cold Chamber Die casting Die DesignThe die is a complex device that has to fulfill a multitude of functions. It defines the general geometry of the part and has a strong influence on the dimensional variations from shot to shot. The use of fixed or moveable cores adds to the flexibility to cast complex, near net shapes. The geometry of the runner and gate system determines the die filling characteristics. The thermal conditions in the die determine thesolidification of each part and thereby the microstructure and quality. Over a large number of shots, the heat Transfer characteristics of the die determine the attainable cycle time.

6 The die is fitted with a system to eject the part after solidification. Course_MgCOM2006, Montreal 2323 Cold Chamber Die casting Die Course_MgCOM2006, Montreal 2424 Cold Chamber Die casting Die Materials steel resistant to thermal shock (commonly, H13 steel or a steel with similar qualities) H13 premium quality steel is commonly supplied to the die manufacturersin a soft annealed condition with spheroidized carbides to improve machinability. After machining, the die cavity parts are hardened andpartially annealed to a hardness typically in the range of 46-48 HRC. Only the die cavity and special parts of the die need to be made of H13steel. This usage typically corresponds to 20-25 % of the die weight. Theremaining parts of the die are made from mild steel and medium carbon steel. Frequently, standardized unit dies are used, especially for smallercastings with relatively simple geometries. Such unit dies consist of themain frame of the die, including the ejector system.

7 The die cavity inserts can be exchanged, and the same unit die can thusbe used for a number of different castings. MAGNESIUM die casting alloys contain less heat per unit volume than aluminium alloys, and the solubility of iron in the molten metal is very leads to a considerably longer lifetime for the dies used for MAGNESIUM , a factor of two or more being quite Course_MgCOM2006, Montreal 2525 Cold Chamber Die casting Part Design Section thickness-1-4 mm due to excellent die filling characteristics- Uniform to avoid local hot spots causing solidification shrinkage- Gradual change in section thickness Easy die filling- Round edges and cornersto facilitate smooth filling Rib for strengthening- Strength and stiffen parts instead of increasing section thickness Local overheating- Direct impact of molten metal at high speed causing local overheating of the die especially at small protrusions Draft Angle- Normally 2-5 degrees- Possibly 1-3 degrees, or even zero draft due to low thermal contraction of Mg Short Course_MgCOM2006.

8 Montreal Chamber Die casting - ProcessPQ2 DiagramShort Course_MgCOM2006, Montreal 2727 Cold Chamber Die casting Max Metal PressureMetal Pressure, pmNADCA1 The pressure required to force molten metal through the die s gateShort Course_MgCOM2006, Montreal 2828 Cold Chamber Die casting Max Metal PressureNADCA1 Short Course_MgCOM2006, Montreal 2929 Cold Chamber Die casting Max Metal PressureNADCA1 Short Course_MgCOM2006, Montreal 3030 Cold Chamber Die casting Max Metal Pressure116 Short Course_MgCOM2006, Montreal 3131 Cold Chamber Die casting Max. Fill RateNADCA2 Short Course_MgCOM2006, Montreal 3232 Cold Chamber Die casting Max. Fill Rate212 Short Course_MgCOM2006, Montreal 3333 Cold Chamber Die casting Theoretical Fill Rate3 NADCAS hort Course_MgCOM2006, Montreal 3434 Cold Chamber Die casting Fill Time3 NADCAS hort Course_MgCOM2006, Montreal 3535 Cold Chamber Die casting Theoretical Fill Rate3123 Short Course_MgCOM2006, Montreal 3636 Cold Chamber Die casting Metal Pressures for Max and Min Gate Velocities4 ,5 NADCA7 Short Course_MgCOM2006, Montreal 3737 Cold Chamber Die casting Metal Pressures for Max and Min Gate Velocities4 ,5 40 - 85 m/s (1600 - 3390 in/sec) for typicalMg die castings(Al: 25 -40 m/s, 1000 - 1600 in/secZn.)

9 40 55 m/s, 1600 2160 in/sec ) 100 m/s (4000 in/sec) for thin-wall castings less than 30 m/s for casting with 4-5 mmwall thicknessNADCAS hort Course_MgCOM2006, Montreal 3838 Cold Chamber Die casting Metal Pressures for Max and Min Gate Velocities4 ,545123 NADCAS hort Course_MgCOM2006, Montreal 3939 Cold Chamber Die casting PQ2 DiagramNADCA(minimum)1234567 Short Course_MgCOM2006, Montreal 4040 Cold Chamber Die casting Gate Area )2(gpcQAdg=Q: volume flow ratep: metal pressurecd: constant ( )g: gravityShort Course_MgCOM2006, Montreal 4141 Cold Chamber Die casting Gating & Course_MgCOM2006, Montreal 4242 Cold Chamber Die casting Gate Velocity 40 - 85 m/s for typical Mg casting (Al: 25-40 m/s; Zn: 40 55 m/s) 100 m/s for thin-wall castings less than 30 m/s for casting with 4-5 mmwall thicknessNADCA8 Short Course_MgCOM2006, Montreal 4343 Global Die Cast Mg ApplicationsCompany Applications GM FORD Chrysler instrumental panels, clutch housing & piston, transmission stators, glove box door, roof frame, seat frame, pedal bracket, steering column bracket, road wheels, Transfer case, valve cover, electric motor housing IP bracket, sun roof panel, pedal bracket, steering column bracket & component, Transfer case, valve cover, clutch housing, steering wheels air bag housing, steering column bracket, valve cover, steering wheel, instrumental panels, alternator bracket, front headlight retainer Audi BMW Fiat Mercedes-Benz instrumental panels, manual transmission housing wheels, gearbox housing, valve cove seat structure, instrumental panels, steering wheel seat frames, sun roof panel.

10 Steering column component intake manifold Honda Toyota Oil pan, cylinder head cover, wheels, valve cover steering wheels, valve cover, bracket Short Course_MgCOM2006, Montreal 4444 MAGNESIUM Instrument Panel Audi and GM AM60 and AM50 Alloys One-piece die casting vs. 12 steel stampings and plastic parts 30-50% weight reduction Reduced cost More styling flexibilityShort Course_MgCOM2006, Montreal 4545GM G Van Instrument PanelShort Course_MgCOM2006, Montreal 4646GM W Car Instrument PanelShort Course_MgCOM2006, Montreal 4747 MAGNESIUM Seat Structure Fiat and Mercedes AM60 Alloy Total part count reduction 50% weight reduction Reduced assembly operations Dimensional accuracyShort Course_MgCOM2006, Montreal 4848 Alfa Romeo Seat Frames9 Short Course_MgCOM2006, Montreal 4949 MAGNESIUM Oil Pan Honda ACM522 Alloy 35% weight reduction Gasoline-power hybrid car -Insight Best fuel consumption 35 km/literShort Course_MgCOM2006, Montreal 5050 Honda Engine Oil PanShort Course_MgCOM2006, Montreal 5151GM 4 Wheel Drive Transfer CaseShort Course_MgCOM2006, Montreal 5252 Potential Die Cast Mg Applications Transmission housing Road wheels Engine cradle Body panels (door and hood)